Vector fields with hybrid states of polarization and their orbital angular momentum

Orbital angular momentum (OAM), as nature of optical field, has attracted considerable attention, due to its academic interest and potential applications such as quantum information, atomic manipulation, micromanipulation and the biosciences. The well-known OAM carried by an optical field originates from the azimuthal phase gradient of an optical vortex field with a helical phase structure. Here we predict a novel optical OAM, which is induced by curl of polarization. To demonstrate experimentally the above prediction, we present an idea for creating a kind of radial-variant vector fields, which could have all local linear polarization and hybrid states of polarization (SoPs). By specifically arranging the SoPs of the vector fields, new effects and phenomena can be anticipated that can expand the functionality and enhance the capability of optical system. The generated vector fields with the radial-variant hybrid SoPs can carry such a novel OAM. Optical trapping experiments validate that the focused vector fields without any additional phase vortex, as the ring optical tweezers, exert torques to drive the orbital motion of the trapped isotropic microspheres.